Conventionally, in the digital radio communication system, there is used an ARQ (Automatic Repeat reQuest) scheme that retransmits data, which cannot be demodulated due to a propagation path error. The transmission/reception apparatus of this type detects a transmission error of a received signal and sends a retransmission request signal to a radio station of a communication partner when detecting the error. The radio station of the communication partner that received the retransmission request retransmits data corresponding to the retransmission request. Then, this processing is repeated until no error is found in the received signal. A series of these processing is called ARQ.
The configuration of this conventional kind of transmission/reception apparatus will be illustrated in FIG. 1. A transmission/reception apparatus 1 comprises a modulation transmission section 2, a reception demodulation section 3 and a retransmission control section 4 in broad outline. Upon transmission, the transmission/reception apparatus 1 transmits a transmission signal S1 to a modulation section 5 via the retransmission control section 4.
The modulation section 5 performs predetermined modulation processing to the transmission signal S1 to form a modulation signal, and transmits the modulation signal to a transmission section 6. The transmission section 6 performs predetermined radio transmission processing such as digital/analog conversion processing, up-conversion, transmission power control and the like, to the modulation signal, and transmits the processed signal to an antenna AN 1.
Meanwhile, at a receiving time, the transmission/reception apparatus 1 inputs a received signal obtained via an antenna AN 2 to a reception section 7. The reception section 7 performs predetermined radio reception processing such as signal amplification, down-conversion, analog/digital conversion processing and the like, to the received signal. An error correction section 8 performs predetermined error correction processing to the input data. The error-corrected received data is transmitted to the retransmission control section 4 and an error detection section 9. The error detection section 9 performs CRC (Cyclic Redundancy Check) to detect an error of the error-corrected received signal, and transmits a detection result to the retransmission control section 4.
When no error is detected by the error detection section 9, the retransmission control section 4 outputs the error-corrected received data input from the error correction section 8 as a received signal S2. In contrast to this, when an error is detected by the error detection section 9, the retransmission control section 4 transmits a retransmission request signal to a radio station of a communication partner at a predetermined timing.
By the way, when data having a propagation path error is retransmitted using the aforementioned ARQ scheme, substantial transmission efficiency decreases by an amount corresponding to the repetitions of retransmissions. That is, the greater the number of retransmissions, the more extra transmissions, and so communication capacity used in actual signal transmission decreases, so that transmission efficiency decreases.
Thus, the conventional transmission/reception apparatus has a problem that, when an error occurs in the received data, the radio station of communication partner is requested to retransmit the error data, so that radio resource is used by an amount corresponding to the occurrence of error, and the throughput reduces.